Gasket frame for plastic casting apparatus

ABSTRACT

A frame for mounting a compressible gasket to be used in a plastic casting apparatus is shown. A stiff frame having an inner perimeter upon which a gasket strip is mounted seals a casting zone between two, flat, closely adjacent glass surfaces. A gap between ends of the gasket strip provides a feed zone through which a conduit carrying plastic casting fluid is inserted. A lever mounted on the frame is rotated to cause ends of the gasket strip to abut one another when sealing of the casting zone is desired.

111 Unite States Patent 1 1 spasms [72] Inventors John 0. Beattie [56] Reference Cited Fr F Ol G h b th f UNlTED STATES PATENTS 8:? 2,390,129 12/1945 Shobert 249/82 x 2,734 227 2/1956 Costick et al.. 18/42 X [21] Appl. No. 765,554 [22] Filed 0&7, 1968 3,341,647 9/1967 Aberle 264/325 [45] Patented Sept. 28, 1971 Primary Examiner.|. Spencer Overholser [73] Assignee The Polycast Corp. Assistant Examiner-L. R. Frye Stamford, Conn. Attorney-Curtis, Morris & Safford [54] ME FOR PLASTIC CASTING ABSTRACT: A frame for mounting a compressible gasket to be used in a plastic casting apparatus is shown. A stiff frame 5 Claims, 5 Drawing Figs. h I

avmg an mner per1meter upon wh1ch a gasket stnp 1s [52] U.S.Cl 249/160, mounted seals a casting zone between two, flat, closely ad- 18/38 jacent glass surfaces. A gap between ends of the gasket strip [51] Int. Cl B4lb11/04 provides a feed zone through which a conduit carrying plastic [50] Field of Search 249/79,80, casting fluid is inserted. A lever moumted on the frame is 81, 160, 161, 162, 163, l64; 18/4 M,38,42 M, DIG. 31,DlG.47;264/26l,263,313, 331

rotated to cause ends of the gasket strip to abut one another when sealing of the casting zone is desired.

PATENTED8EP28IB7I 350 5 INVENTORS JAMES JAY FERRIS 3 JOHN 0. BEATTIE IY ATTORNEYS GASKET FRAME FOR PLASTIC CASTING APPARATUS This invention relates to an apparatus for casting flat sheets of plastic. More specifically, it relates to a support frame for gaskets sealing the casting zone between two closely adjacent mold surfaces.

Several processes for the casting of flat sheets of synthetic resin are known. A monomer or syruplike partial polymer of a synthetic resin is introduced into a casting zone bounded by two parallel, spaced plates of glass, metal or other relatively smooth, inert material. The plates are spaced apart at their periphery by a gasket of a somewhat compressible material so that shrinkage of the polymerizing sheet can take place without separation of the sheet from the mold surface. Typically these parts are held together forming a mold chamber or cell by suitable clamps or presses and subjected to polymerizing and curing conditions to form the solid sheet. The casting may take place either horizontally as shown in U.S. Pats. Nos. 3,087,197 and 2,328,525 or vertically as shown in U.S. Pats. Nos. 3,165,786 and 2,369,593. In either case a gasket must be arranged between the two plates to establish the proper separation and seal; and provision must be made for filling the thus defined casting zone.

The gasket is often placed by hand, a technique both time consuming and often inaccurate. The resin casting fluid has been fed into the casting zone either through a break in the gasket, or prior to final formation of the cell, i.e. on top of an open plate. Either procedure is clumsy and inefficient, and breakage of the glass mold plates is a common occurrence. Still further, the gasket often is incorporated in the cast plastic or damaged so that a new gasket must be placed in the cell after each casting. Where the casting zone is narrow it is awkward and difficult to reach between the mold surfaces to place gasket strips and there is likelihood of transferring smudges to smooth mold surfaces and therefrom to the surface of the next casting. Complete separation of the mold surface is necessary before a new gasket can be placed. Where the mold surfaces are vertical, gasket placement is yet more difficult and a retainer is required to maintain gasket orientation and avoid misshapen castings or loss of casting fluid due to gasket slippage.

It is is the primary object of this invention to provide a gasket support frame which simplifies the placement of a gasket between the opposing mold surfaces of a casting zone.

It is a further object of this invention to provide a frame having a gasket support including a feed zone for the casting chamber and a closure attachment whereby that feed zone is sealed off.

These and other objects of this invention are achieved by a gasket support frame, the inner perimeter of which describes the locus of points along which a seal is desired. An edge is provided along the inner perimeter upon which a strip of sealing gasket is mounted. Adjacent ends of this inner edge and the ends of the mounted sealing gasket strip are separated; they define a feed zone for introduction of casting fluid into the casting chamber. A closure attachment on the frame permits the gasket ends to be forced against on another to seal off the feed zone.

IN THE DRAWINGS FIG. 1 is a perspective view of the gasket frame between two flat sheets of glass which comprise the mold surfaces. The glass plates are spaced apart for sake of clarity;

FIG. 2 is a side view of the upper right corner of the gasket frame showing details of the feed zone and closure attachment in the open position;

FIG. 3 is a side view of the upper right corner of the gasket frame showing details of the feed zone and closure attachment in the closed position;

FIG. 4 is a section view of the gasket frame taken through the feed zone at line 4-4 of FIG. 3; and

FIG. 5 is a section view of the gasket frame taken at line 5- 5 of FIG. 3.

In FIG. ll reference numerals l0 and 12 refer to vertically positioned, flat plates of glass between which a flat sheet of plastic, methyl methacrylate for example, is cast. Reference numeral 14 refers to frame fabricated from 18 gauge (0.050 inch) by 4 inch stainless steel strip. The strip is rolled to form a rounded outer perimeter 18.

As seen more clearly in FIGS. 2 and 5 the inner perimeter 20 of frame 14 substantially describes the locus of points at which a seal is desired between plates 10 and 12. A strip of gasket material 22 which may be plasticized vinyl chloride, hard rubber or other suitable material is mounted along inner perimeter 20 of frame 14. A slit 211 in gasket 22 provides a tight-fitting recess for the inner edge of frame 14. Other mounting surfaces of varying shape can be provided to establish a firm connection between gasket and frame. One end of gasket strip 22 terminates in dead end area 24 of frame 114 wherein it is tightly wedged. Adjacent to this end gasket strip 22 has a short length 26 normal to the upper horizontal run of gasket designated by numeral 28. The upper right-hand side of frame 14 has recessed inner perimeter 30 which permits relatively free right-to-left movement of end 32 of gasket 22. As discussed further below, this is a flexible boundary of the feed zone. A lever 34 having handle 36, fulcrum 38 consisting of a pin or rivet through the upper portion of frame 14 and sealing arm 40 is mounted at the upper right-hand corner of the frame. When lever 34 is in the open position as shown in FIG. 2 a space 42 between adjacent end portions 32 and 26 of gasket strip 22 permits insertion of feed tube 31 into the casting zone through which a monomer or partial polymer can be supplied. When handle 36 of lever 34 is rotated downwardly, sealing arm 40 contacts gasket end 32 in slit 21 and forces it across feed zone 42 into substantially parallel sealing relationship with length 26 of gasket 22. This is shown most clearly in FIGS. 3 and FIG. 4.

In operation the two glass plates 10 and 12 are brought into close proximity with gasket frame 14 held in close abutting relationship by means of a press or clamps not shown. Handle 34 is in its upward position leaving a feed zone 42 between the ends of gasket strip 22. Tube 31 is inserted into the casting zone defined by the inner walls of plates 10 and 12 and gasket 22 and casting syrup is fed into the space. When the correct inventory of liquid has been added, handle 36 is moved downwardly causing the ends of the gasket strip to abut one another and seal off the casting zone. The cell can then be subjected to polymerizing and curing conditions in accordance with the type of plastic which is being cast.

After casting is finished the cast sheet is removed from the mold surfaces. If the gasket has stuck to the cast plastic a new gasket frame having a new gasket is simply placed between plates 10 and I2 and the process is repeated. If the cast sheet separates from gasket 22 the same gasket can be used over and over again without realigning the gasket and/or touching the inside surfaces of the casting zone.

As shown the gasket is provided with clips 44 which permit it to be hung from a horizontal support and permit casting to take place in a vertical plane. As described in copending application SER. No. 604,242 assigned to the same assignee as this application, substantial economies are achieved with such an apparatus. The gasket frame, however, can be used in horizontal cells such as those shown in the patents noted above. The gasket frame is easy to handle by virtue of its stiffness and the gasket is securely held in place by frictional or other mating engagements on the inner perimeter of the frame.

What is claimed is:

H. In an apparatus for casting a plastic fluid between two flat closely adjacent, mold surfaces, the peripheral sealing surfaces of which are in close facing relationship, a sealing gasket support frame having provision for filling of the casting zone between said flat surfaces with liquid, comprising: a sealing gasket support frame having an inner perimeter which substantially describes the locus of points along which a seal is desired; a sealing gasket strip firmly supported on said inner perimeter, an end of said gasket being movable relative to an 3. The apparatus of claim 1 wherein said means for causing adjacent ends of gasket strip to seal against one another comprises a lever having a handle, a fulcrum in said frame and sealing arm which contacts one end of said sealing gasket strip and clamps it against the other end of said sealing gasket strip upon application of force on said lever handle.

4. The apparatus of claim 1 wherein said frame is rectangular in shape and said liquid feed zone is located at a corner thereof.

5. The apparatus of claim 4 wherein the inner perimeter adjacent to said feed zone on a first side thereof terminates in a short length leading away from said casting zone, the inner perimeter adjacent to said feed zone on the second side thereof has a recessed portion which permits free movement of an end of said sealing gasket strip, and a lever fulcrumed on said frame and having a handle and sealing arm is positioned to engage the freely movable end of said sealing gasket strip and upon application of force to the handle cause said length to abut in substantially parallel sealing relationship the gasket strip on the short terminating length of the first side. 

1. In an apparatus for casting a plastic fluid between two flat closely adjacent, mold surfaces, the peripheral sealing surfaces of which are in close facing relationship, a sealing gasket support frame having provision for filling of the casting zone between said flat surfaces with liquid, comprising: a sealing gasket support frame having an inner perimeter which substantially describes the locus of points along which a seal is desired; a sealing gasket strip firmly supported on said inner perimeter, an end of said gasket being movable relative to an adjacent end thereof to create a feed zone for insertion of liquid feed means into the casting zone between said flat surfaces; and closure means associated with said frame to cause said adjacent ends of said gasket strip to abut against one another and close off said feed zone when complete sealing is required.
 2. The apparatus of claim 1 wherein the adjacent ends of said gasket strip at said feed zone are in substantially parallel orientation thereby permitting a gasket strip seal along a length thereof.
 3. The apparatus of claim 1 wherein said means for causing adjacent ends of gasket strip to seal against one another comprises a lever having a handle, a fulcrum in said frame and a sealing arm which contacts one end of said sealing gasket strip and clamps it against the other end of said sealing gasket strip upon application of force on said lever handle.
 4. The apparatus of claim 1 wherein said frame is rectangular in shape and said liquid feed zone is located at a corner thereof.
 5. The apparatus of claim 4 wherein the inner perimeter adjacent to said feed zone on a first side thereof terminates in a short length leading away from said casting zone, the inner perimeter adjacent to said feed zone on the second side thereof has a recessed portion which permits free movement of an end of said sealing gasket strip, and a lever fulcrumed on said frame and having a handle and sealing arm is positioned to engage the freely movable end of said sealing gasket strip and upon application of force to the handle cause said length to abut in substantially parallel sealing relationship the gasket strip on the short terminating length of the first side. 